Pneumatic control of pressure pouring ladle



April 1970 M. J. DIAMOND ETAL 3,504,825

PNEUMATIC CONTROL OF PRESSURE POURING LADLE Filed Aug. 15. 1966COMPRESSED AIR SUPPLY rwL DIFFERENTIAL PRESSURE TRANSMITTER DWFERENTMLPRESSURE TRANSMITTER VENT IN VEN'J'OR S ATTORNEY United States Patent3,504,825 PNEUMATIC CONTROL OF PRESSURE POURING LADLE Milton J. Diamond,Saginaw, Mich., and Robert J. Kinsey, Danville, Ill., assignors toGeneral Motors Corporation,

Detroit, Mich., a corporation of Delaware Filed Aug. 15, 1966, Ser. No.572,259 Int. Cl. B22d 17/32; F27d 3/14 US. Cl. 22261 Claims ABSTRACT OFTHE DISCLOSURE A pneumatic control circuit develops a pressure signal asa function of metal height in the pouring spout and controls the ladleair pressure to maintain constant metal height. A differential pressuresensor in the ladle air supply line controls a vent to relieve airpressure when metal is added to the ladle.

This invention relates to pneumatic control apparatus for pressurepouring ladles and articularly to pneumatic control systems forcontrolling the air pressure in a ladle.

Pneumatic ladles for pouring molten metal into foundry molds comprise anair-tight ladle having a pouring spout attached at the bottom of themain body of the ladle and having a receiving spout also attached at thebottom of the ladle, the open end of both spouts being near the top ofthe ladle. Air pressure is supplied to the top of a ladle by an airsupply line and the air pressure acting on the surface of the moltenmetal within the ladle serves to force the metal out of the pouringspout. The rate at which the metal pours from the spout into the molddepends upon the height of the metal above the lip of the spout, whichin turn depends upon the amount of air pressure within the ladle. Formost pouring operations, it is important to maintain a constant pouringrate and hence a constant metal height in the spout because there is anoptimum rate at which the metal should enter the mold and because theamount of metal delivered to each mold is often measured by the rate offlow and the duration of flow. When the metal within the ladle is nearlyexpended, it is desirable to pour in additional metal through thereceiving spout without interrupting the normal pouring function of theladle. However, if the additional metal rises within the ladle, the airentrapped therein tends to increase in pressure and control means mustbe provided to relieve the excess air without disturbing the criticalpressure balance which controls the pouring rate.

Control systems for the control of ladle air pressure previously havebeen proposed, some of which are not sufliciently accurate and some ofwhich are exceedingly complicated, thereby being expensive to installand expensive to maintain. Previous control systems have also failed totake into account the necessity of properly relieving excess airpressure from the ladle when additional metal is poured into thereceiving spout.

It is an object of this invention therefore, to provide improved controlmeans for a pneumatic ladle.

A further object of the invention is to provide improved and simplifiedpneumatic control means for a pneumatic ladle.

Another object is to provide a simple control for a pneumatic ladlewhich is capable of reliably maintaining a constant rate of flow fromthe pouring spout even while additional metal is being supplied to theladle.

An additional object is to provide a control means for a pneumatic ladlewhich accommodates the excess pressure created when additional metal issupplied to the ladle.

The invention is carried out by providing means for detecting the metalheight within the pouring spout, means for developing a signal which isa function of the metal height and means responsive to the signal forcontrolling the air pressure within the ladle to maintain a desiredmetal height.

The invention is further carried out by providing float means detectingthe metal height within the pouring spout of a ladle, valve meanscontrolled by the float for passing air through an orifice means at arate which is a function of the metal height so that a pressure signaldeveloped across the orifice means is proportional to the air flow rate,and means responsive to the pressure signal for adjusting a regulatingvalve in the air supply means to the ladle. In addition, the inventionprovides that the orifice means comprises a plurality of selectivelyutilized orifices, each corresponding to a different desired metalheight.

In addition, the invention further provides a controllable vent means inthe ladle supply line to relieve excess pressure from the ladle duringrefilling thereof.

The invention is further carried out by providing means in the airsupply line to the ladle for relieving excess pressure from the ladleduring refilling thereof including means for detecting the amount ofexcessive pressure in the ladle and for controlling the degree ofventing which is required to maintain the desired metal height in thepouring spout. The above and other advantages will become more apparentfrom the following description taken in conjunction with the drawingwhich is a schematic diagram of a pneumatic control apparatus for apneumatic ladle according to the invention.

Referring to the drawing, there is shown a pneumatic ladle 10 having areceiving spout 12 and a pouring spout 14. An upstanding lip or dam 15is formed at the end of the pouring spout 14. A mold 16 is disposedadjacent the pouring spout 14 to receive the molten metal issued fromthe spout. As stated above, the rate at which the metal issues from thespout is dependent upon the height of the metal in the spout. An airline 18 is communicably connected to the top of the ladle. A pressurecontrol system monitors the rate at which the air is supplied to orwithdrawn from the ladle. A part of the pressure control system is afloat 20 in the pouring spout arranged to detect the height of the metalin the spout by floating on the metal Within the spout, and the float ismechanically connected to an air regulating valve 22. A source 24 ofcompressed air having a pressure of p.s.i., for example, is connected tothree pressure regulators 26, 28 and 30. The regulators feed air to apressure control line 32, a pressure transmitter line 34 and an airsupply line 36. Air floating through the air supply line 36 goes to agauge 38, a diaphragm operated control valve 40, an orifice orrestriction 42 and finally flows to the ladle via the air line 18. Thecontrol valve 40 is capable of supplying air to the ladle or venting airfrom the ladle depending on the valve posi tion. A vent valve 44 isconnected to the air line 18 between the orifice 42 and the ladle 10,and is arranged to controllably vent air from the air line to theatmosphere. A pressure differential transmitter 46 is connected acrossthe orifice 42 with the high pressure side of the transmitter connectedat the side of the orifice closest to the ladle.

The differential pressure transmitter 46 has an output line connected toa diaphragm 48 which operates the vent valve 44. The transmitter 46 is adevice well known in the art which serves to provide an amplified outputpressure which is proportional to the input pressure differential. Theressure control line 32 extending from the pressure regulator 26contains a gauge 50 and the air flow control valve 22 in series with anorifice means 52. The orifice means 52 comprises a pair of orifices orrestrictions 54 and 56 in parallel having one side connected to the airline from the air flow valve 22, and other side being vented toatmosphere. One orifice 54 is used to control the high metal height inthe pouring spout while the other orifice 56 of a smaller size controlsthe low metal height corresponding to a non-pouring condition. Eachorifice has a valve 58 and 60 in series therewith for selectivelyadmitting air to the orifices. The valve 58 and 60 are preferablysolenoid controlled and are arranged so that one valve is normallyopened while the other is normally closed. Other means of controllingthe valves may be substituted, however. The orifices 54 and 56 are ofdifferent sizes so that for a given air fiow through the air flow valve22, different pressure differentials will be created across the orificemeans depending on which valve, 58 or 60, is open.

The pressure transmitter line 34 extends from the pressure regulator 28to a gauge 62 and to a difierential pres sure transmitter 64. Inputlines 66 of the differential pressure transmitter 64 extend to eitherside of the orifice means 52 so as to detect the pressure signal fromthe orifice means. The differential pressure transmitter 64 amplifiesthe pressure signal and supplies an output to the dia phragm 68 whichoperates valve 40 in the air supply line. Gauge 70 indicates the outputpressure of the transmitter 64.

In operation, for the condition when the ladle is pouring molten metalinto the mold 16, the position of the float 20 is determined by theheight of the metal and the float in turn controls the position of theair fiow valve 22 in the pressure control line 32. The rate of air flowthrough the pressure control line and the orifice means 52 is thereforecontrolled by the position of the float operated air control valve. Forthe pouring condition, the valve 60 for the low height orifice 56 isclosed and the valve 58 for the high height orifice 54 is open so thatthe pressure developed across the high height orifice 54 is proportionalto the air flow therethrough. This pressure differential signal issupplied to the input 66 of the differential pressure transmitter 64.The latter device amplifies the pressure signal and the output thereofcontrols the diaphragm operated valve 40 in the air supply line so as tocontrol the air flow therethrough in a manner to maintain the necessaryladle pressure to keep the metal height relatively constant. That is,when the metal height rises slightly from its desired level, thechanging position of the fioat 20 causes the valve 22 to open furtherthan its normal position to increase the air flow through the orifice54. The resultant increase in pressure thereacross signals thetransmitter 64 to increase the pressure on the diaphragm 86 which movesthe valve 40 toward its closed position, thereby reducing the pressureto the ladle 10 and lowering the metal height in the pouring spout 14 toits normal level.

When it is desired to stop pouring from the ladle, the valves in theorifice means are returned to normal condition (valve 58 closed andvalve 60 open) so that the air will pass through the small low heightorifice 56 and the pressure developed thereacross will be greater thanit was through the high height orifice. This. therefore increases thepressure signal which causes the diaphragm operated valve 40 to close,and if necessary, the valve 40 will be turned by the diaphragm toventing position to allow air to escape from the ladle until the metalheight reaches the desired low level called for by the pressure signal,whereupon any variation thereafter in the metal height will becontrolled by the system just described. The low level is preferablyjust below the top of the lip or dam 15 so that no pouring can occur atthat level, yet a change to the high level for pouring can be rapidlyaccomplished with a minimum air pressure increase in the ladle.

When it is desired to replenish the molten metal in the ladle 10, newmetal is poured into the receiving spout 12 causing the level of themetal within the ladle to rise, consequently causing the air within theladle to become further compressed so that its pressure increases withthe result that, in the absence of further control means, the metalheight in the pouring spout would increase. The rising motion of thefloat, however, will cause the control system to turn the valve 40 toventing position so that the excess air within the ladle will berelieved by passing from the ladle through air line 18 and through thevalve 40. It has been found, however, that this arrangement forrelieving excess air pressure in the ladle is not adequate whenadditional metal is supplied to the ladle at a high rate. Accordingly,an equalizing system is provided to prevent a large increase in theladle pressure. The air flowing from the ladle to the valve 40 passesthrough the orifice or restriction 42 and generates a pressure differential signal which is detected and amplified by the differential pressuretransmitter 46. That device signals the diaphragm 48 to open the ventvalve 44 in an amount proportional to the valve of the orifice pressurediiferential to thereby vent the excess air from the ladle at a ratewhich will maintain control of the metal height. It will then bepossible to pour from the ladle in the normal controlled fashion evenwhile new metal is being provided through the receiving spout.

It will be seen then that the system described herein provides a simple,accurate and improved pneumatic control system for a pneumatic ladle.The specific apparatus described above is the preferred embodiment ofthe invention and the scope of the invention is not intended to belimited thereto, but rather is limited only by the following claims.

We claim:

1. Apparatus for controlling the height of metal in the pouring spout ofa pneumatic pouring ladle comprising supply means for supplying airpressure to the ladle, pressure regulating means in the supply means,means for developing a signal responsive to metal height in the pouringspout, and means responsive to said signal for controlling the pressureregulating means according to said signal whereby the metal height ismaintained at a desired value, wherein the means for developing a signalcomprises orifice means, a compressed air supply connected to one sideof the orifice means, the other side of the orifice means being ventedto atmosphere, and means for controlling the said air supply to theorifice means in accordance with the height of the metal in the pouringspout whereby the pressure signal developed across the orifice means isa function of the metal height.

2. Apparatus as defined in claim 1 wherein the orifice means comprises aplurality of orifices of different sizes selectively connectable to thecompressed air supply, whereby a plurality of desired metal heights maybe selected.

3. Apparatus as defined in claim 1 wherein the means responsive to saidsignal for controlling the pressure regulating means according to saidsignal comprises a difierential pressure transmitter having its inputconnected to said signal and its output connected to the pressureregulating means.

4. Apparatus as defined in claim 3 wherein the means for controlling thesaid air supply to the orifice means in accordance with the height ofthe metal in the pouring spout comprises an air regulating valve betweenthe compressed air supply and the orifice means and means for detectingthe height of the metal and for controlling the air regulating valve.

5. Apparatus as defined in claim 4 wherein the means for detecting theheight of the metal is a fioat in the pouring spout connected to the airregulating valve.

6. Apparatus for controlling the height of metal in the pouring spout ofa pneumatic pouring ladle comprising supply means for supplying airpressure to the ladle, pressure regulating means in the supply means,means for developing a signal responsive to metal height in the pouringspout, and means responsive to said signal for controlling the pressureregulating means according to said signal whereby the metal height ismaintained at a desired value, including vent means between the pressureregulating means and the ladle for controllably venting air from theladle so that when metal is added to the ladle, air displaced therebywill be vented, and detecting means including a conduit connected tosaid supply means for directly sensing air pressure in the ladle inexcess of that called for by the said signal, the detecting meanscontrolling the vent means.

7. Apparatus as defined in claim 6 wherein the detecting means comprisesan orifice in the supply means so that a pressure differential willoccur across the orifice when air passes from the ladle to the supplymeans, and further comprises a differential pressure transmitter meansconnected across the orifice and controllably connected to the ventmeans for sensing the pressure differential and accordingly controllingthe vent means.

8. In a system for controlling metal height in the pouring spout of apressure ladle, air line means for supplying air pressure to the ladleand relieving pressure from the ladle, means for supplying a regulatedair pressure to the air line, a vent means in the air line means forbleeding excess pressure from the ladle, and detecting means includingconduit means connected to said air line means for directly sensing anexcess of air pressure in the ladle over the regulated air pressure, thedetecting means being connected to the vent means to eifect controlthereof.

9. In a system for controlling metal height in the pouring spout of apressure ladle, air line means for supplying air pressure to the ladleand relieving pressure from the ladle, a vent means in the air linemeans for bleeding excess pressure from the ladle, and detecting meansfor sensing excess pressure in the ladle, the detect- References CitedUNITED STATES PATENTS 716,321 12/1902 Webster 222397 X 1,714,296 5/1929Carlson 222396 1,8 13,381 7/ 1931 Carrin gton 222397 X 2,816,334 12/1957Edstrand 22264 X 3,229,337 l/ 1966 Holz et al 222399 X 3,286,311 11/1966Rhoads 22261 3,347,427 10/ 1967 Willis 222399 3,058,180 10/1962 Port etal. 164-456 3,384,150 5/1968 Newsome 164155 ROBERT B. REEVES, PrimaryExaminer F. R. HANDREN, Assistant Examiner US. Cl. X.R.

